Radar measurement extraction in the presence of sea-surface multipath

In the presence of sea-surface multipath monopulse radar signals from a low elevation target have three alternative paths in addition to the direct (radar-to-target) path due to reflections from the sea surface. The specular reflection causes significant signal fading. The diffuse reflection causes an approximately constant bias to the in-phase component of the monopulse ratio, which is the standard extractor of the direction of arrival (DOA) in the monopulse processing. The diffuse reflection also causes higher standard deviation to the in-phase component of the monopulse ratio. We propose a maximum likelihood (ML) angle extraction technique for low elevation targets of known average signal strength having a Rayleigh fluctuation. The results show that this method reduces the error of the estimated angle compared with the conventional monopulse ratio estimator. Subsequently, the ML angle extractor is modified for the unknown average signal strength case. This modified angle extractor has only a small performance degradation compared with the known average signal strength case, but it performs much better than the monopulse ratio based estimator. An algorithm to calculate the accuracy of the estimated angle (or height) is also presented. This angle extractor reduces the root-mean-square error (RMSE) by more than 50% in the signal processing stage when used in a low flying target tracking scenario. The same algorithm can be used to track sea skimmers.     

A Controllable and Observable Protein Cystallization Facility.

A Controllable and Observable Protein Crystallization Facility (ACOP) was developed in 1999 for space experiment in the Get Away Special canister of Space Shuttle. To regulate the vapor diffusion rate, in a crystallization chamber, five cells each containing precipitant solution of different concentrations, exposed to one protein cell in turn. Five layers of chambers were overlapped coaxially. The crystallization process was observed and recorded by digital cameras. Structure of facility and result of image sequence were given.     

Mutagenic effects of heavy ion radiation in plants.

Genetic and developmental effects of heavy ions in maize and rice were investigated. Heavy particles with various charges and energies were accelerated at the BEVALAC. The frequency of occurrence of white-yellow stripes on leaves of plants developed from irradiated maize seeds increased linearly with dose, and high-LET heavy charged particles, e.g., neon, argon, and iron, were 2-12 times as effective as gamma rays in inducing this type of mutation. The effectiveness of high-LET heavy ion in (1) inhibiting rice seedling growth, (2) reducing plant fertility, (3) inducing chromosome aberration and micronuclei in root tip cells and pollen mother cells of the first generation plants developed from exposed seeds, and (4) inducing mutation in the second generation, were greater than that of low-LET gamma rays. All effects observed were dose-dependent; however, there appeared to be an optimal range of doses for inducing certain types of mutation, for example, for argon ions (400 MeV/u) at 90-100 Gy, several valuable mutant lines with favorable characters, such as semidwarf, early maturity and high yield ability, were obtained. Experimental results suggest that the potential application of heavy ions in crop improvement is promising. RFLP analysis of two semidwarf mutants induced by argon particles revealed that large DNA alterations might be involved in these mutants.     

Radiotomographical Detection of Ionosphere Disturbances Caused by Ground Explosions

Long-lived local disturbances of the ionospheric density over the site of ground industrial explosions were detected by the ionosphere radiotomography method. It is assumed that the density anomalies arise because of the initiation of vortex motion in a neutral component after acoustic impulse passage.     

The gravity-darkening of the main-sequence components of spectral types A,F and G in detached close binary systems

From analysis of the photometric ellipticity effect in seven well-understood detached close binary systems, empirical values of the exponent α of gravity-darkening have been practically deduced for eleven main-sequence components of spectral types A, F and G which should cover the range of structural change (from radiative to convective) in stellar atmospheres. The result indicate that values of the exponent diminish gradually with decreasing effective temperatures from α ～ 1.0 for radiative atmospheres with T > 8500 K to α = 0.2 ～ 0.3 for convective atmospheres with T < 6500 K, in spite of some uncertainty in the reflection correction process.     

On the Convergence of Iterative Orthogonalization Processes

Polar decomposition of matrices is used here to investigate the convergence properties of iterative orthogonalization processes. It is shown that, applying this decomposition, the investigation of a general iterative process of a certain form can be reduced to the investigation of a scalar iterative process which is simple. Three known iterative orthogonalization processes, which are special cases of the general process, are analyzed, their convergence rate (order) is determined, and their range of convergence is established in terms of the spectral radius of the modulus of the matrix which is being orthogonalyzed.     

The diffuse soft X-ray sky

The current status of the investigation of the soft X-ray diffuse background in the energy range 0.1–2.0 keV is reviewed. A consistent model, based on the soft X-ray brightness distribution and the energy spectrum over the sky, is derived. The observed diffuse background is predominantly of galactic origin and considered as thermal emission for the most part from a local hot region of temperature ≈10⁶ K which includes the solar system. Several pronounced features of enhanced emission are interpreted in terms of hot regions with temperatures up to 3×10⁶K, some of which are probably old supernova remnants. The properties of the soft X-ray emitting regions are discussed in relation to the observational results on O vi absorption.     

Experimental and theoretical analysis of the influence of gravity at the cellular level: a review.

The present paper is a review of the experimental investigations published in the literature and performed by the authors on space vehicles. The paper also gives an analysis of theoretical concepts concerning gravitational effects on the cell. Taking this into account, the authors put forth a hypothesis that free-living unicellular organisms are indifferent to variations in the magnitude and direction of the gravitational field.     

Effects of muscle electrostimulation during simulated weightlessness

In a 45-day experiment test subjects were exposed to bed rest with their heads down at -4 degrees C. Twice a day their muscles of the stomach, back, femur, and shin were stimulated with electric current for 25-30 min. The value of muscle tension was close to their maximum voluntary contraction. The main objective was to prevent muscle atrophy and to maintain their trophic and functional state. Physiological measurements were carried out together with morphological, cytochemical, and biometric evaluations. The tissue removed during biopsy from M. soleus 7 days before the test and on the 30th hypokinetic day was used as substrate. Electrostimulation affected favourably the tone and strength of muscles as well as their static and dynamic endurance. Morphological studies showed a positive effect of electrostimulation on the muscle tissue, preventing the development of atrophic processes. During the first post-hypokinetic day orthostatic tolerance increased.